1. Field of the Invention
This invention relates to the field of material deposition, and more specifically, to the deposition of one or more semiconductor layers/films onto a substrate member.
2. Description of the Related Art
It is known in the field of semiconductor manufacturing that semiconductor material be selectively deposited onto a substrate member. In so doing, it is known that an in-line horizontal, and in-line vertical, or a circular assembly of vacuum deposition chambers may be used wherein the substrate member is sequentially moved from one chamber to another as is needed to achieve a desired sequence of semiconductor layers on the substrate member.
It is usual that the limited internal volume of a vacuum deposition chamber limits the physical size of a substrate member that can be inserted into the chamber(s), and upon which semiconductor material may be deposited.
It would be desirable to provide a means whereby a substrate holder would enable a larger area of substrate to be operated upon by a deposition chamber(s).
This invention provides a substrate cassette for use in a single chamber deposition system for use in an in-line multiple chamber deposition system, and for use in a circular multiple chamber or cluster tool deposition system.
A substrate cassette in accordance with this invention contains two physically spaced and parallel reels, either of which can be designated as the supply reel, whereupon the other reel becomes the take-up reel. A relatively long and linear web of flexible substrate material (for example, a stainless steel or plastic substrate material that is about 0.003-inches thick), about 1-foot wide and about 100-feet long, is wound about the supply reel, and the 1-foot wide exposed end of the web is connected to the take-up reel. In this way, a relatively short length (for example, 1-foot by 1-foot square) of the substrate material is supported in a deposition plane, usually either vertical or a horizontal plane, that lies between the supply reel and the take-up reel.
In an embodiment of the invention, a protective backing web is provided adjacent to the back side of the substrate web, this protective web operating to protect a deposition layer(s) that is carried by the deposition side of the substrate web.
In an embodiment of the invention wherein a single layer of a semiconductor material is to be deposited on substantially the entire 100-foot length of the substrate web, the substrate cassette of the invention is placed in a deposition chamber, and a relatively short 1-foot length of the substrate is exposed to the deposition volume of the deposition chamber. A reel-to-reel servo system then operates to advance the substrate from the supply reel to the take-up reel at a relatively slow but constant speed, while maintaining a constant tension in the web, as substantially the entire 100-foot length of the substrate web receives a deposited layer; for example, a semiconductor layer, onto one side surface of the web. The end result is a take-up reel having about 100 feet of substrate material that contains a single deposition layer.
Embodiments of the invention provide for the deposition of multiple layers onto the long substrate web.
In a first embodiment wherein multiple layers are produced, a first layer is deposited on the entire 100 foot length of the substrate web as above described. The substrate web is then rewound from the take-up reel back onto the supply reel, and the above-described process is repeated in order to deposit a second and usually different layer onto the first layer. Of course, this process can be repeated N times in order to deposit N layers onto the 100 foot length of the substrate web. While it may be preferred to rewind the substrate web between use of the cassette in another deposition chamber, it is within the spirit of the invention to eliminate this rewind step, and to rewind the substrate web from the take-up reel to the supply reel as deposition of a second layer is taking place in the second deposition chamber.
In a second embodiment wherein multiple layer structures are produced, the substrate cassette of the invention is placed in a first deposition chamber, and a relatively short length of the substrate is exposed to the deposition volume of the first deposition chamber. A first layer is then deposited on this first length of the substrate web. The cassette is then moved to a second deposition chamber, and a second layer is deposited on the substrate""s first length of the substrate web. In this manner, the cassette is moved between a number of deposition chambers as a like number of layers are deposited on the first length of the substrate web. Once all layers have been deposited on the first length of the substrate web, a reel-to-reel servo system operates to step advance the substrate web to expose a second length of the substrate at the deposition operative position between the two reels. The cassette is then recycled through the deposition chambers to produce a second multiple layer structure on the substrate second length. In this embodiment of the invention, when the substrate has been completely wound from the supply reel to the take-up reel, the take-up reel contains a number of individual substrate areas, each individual substrate area containing one multiple layer structure. For example, when the substrate web is about 100-feet long and about 1 foot wide, and when each individual substrate deposition length is about 1 foot long, the finished web contains as many as 100 individual multiple layer structures, each measuring about 1 foot by 1 foot.
In a preferred embodiment of the invention, a number of vacuum deposition chambers are mounted in a generally circular configuration so as to occupy a generally common horizontal plane, and a centrally-located vacuum chamber contains a robotic arm that is mounted at a central location relative to the deposition chambers. This robotic arm periodically rotates in the common plane to thereby step transport the substrate cassette from one deposition chamber to another deposition chamber, as multiple layers are vacuum deposited on the substrate member. In another embodiment of the invention, the multiple vacuum deposition chambers are arranged in a generally linear or in-line fashion, either horizontal or vertical, and a transport means operates to step transport the substrate cassette through the deposition chambers.
A non-limiting use of a single vacuum chamber deposition system is in the manufacture of a thin semiconductor, such as an amorphous silicon layer, a thin film amorphous silicon alloy layer, a micro-crystalline silicon, or a poly-crystalline silicon layer on a relatively long/narrow and inert substrate web.
A non-limiting example of the use of such a linear or circular vacuum deposition chamber configuration is in the manufacture of n-i-p semiconductor structures, such as amorphous silicon, micro-crystalline silicon or poly-crystalline type semiconductor on a relatively long/narrow and inert substrate web. In this use, a first vacuum chamber is used to deposit a n-type layer on the substrate member, a second vacuum chamber is used thereafter to deposit an intrinsic layer on the n-type layer, and a third vacuum chamber is used thereafter to deposit a p-type layer on the intrinsic layer, or three such vacuum chambers can be used in the opposite sequence to produce p-i-n semiconductor structures.
As will be appreciated, deposition chambers other than those above described can be used, as desired, in order to manufacture virtually any type of semiconductor structure. For example, a deposition chamber can be used to deposit a first metal contact layer on the substrate web prior to deposition of the above described first semiconductor layer, and yet another vacuum deposition chamber can be used to deposit a second metal contact layer on the last semiconductor layer; for example, by using techniques such as, but not limited to, metal vapor deposition and metal evaporation.
The present invention provides a new and unusual substrate cassette or substrate magazine physical format that contains a relatively long, narrow and flexible substrate web that is length advanced through a single station deposition system, or through the various stations of a multiple station deposition system.
While the substrate cassette of this invention finds utility in both single station vacuum deposition systems and multiple station vacuum deposition systems, the spirit and scope of this invention is not to be limited thereto, since substrate cassettes of this invention are useful in virtually any deposition system wherein a layer is deposited on the substrate web as the substrate web moves from a first reel, through a deposition area, and then onto a second reel.
As a feature of the present invention, the substrate cassette of the invention includes a first idler roller that is associated with the first reel, and a second idler roller that is associated with the second reel. While the effective diameters of the two reels change as the substrate web moves from one reel to the other, the substrate web is guided by the two idler rollers as it moves between the two reels, and the two idler rollers are structurally mounted to accurately establish a deposition plane whereat deposition takes place along substantially the entire length of the substrate web.
As another feature of the present invention, each of the two reels within the substrate cassette is driven by its own electrical motor, and these two motors are servo-controlled so as to maintain a constant tension within the relatively short length of the substrate web that extends between the two idler rollers, thus ensuring that this short length of the substrate web is always maintained in one, non-varying, deposition plane.
As a feature of the invention the two ends of the substrate web are clamped to the respective two reels by the operation of an axially split cylindrical cover that is radially compressed to capture an end of the substrate web against the underlying cylindrical surface of a reel.
These and other features and advantages of the invention will be apparent to those of skill in the art upon reference to the following detailed description, which description makes reference to the drawing.